Polyimide resins are widely used due to their heat resistance and electrical insulation. However, polyimide resins have several drawbacks including poor flexibility because of rigidity, difficulty to use because of high glass transition temperature (Tg), and low solubility in organic solvents. To overcome these drawbacks, Patent Document 1 proposes a silicone-modified polyimide resin.
Also, polybenzoxazole resins have excellent heat resistance and electrical insulation and are thus widely used as resin varnishes for electronic parts and flexible printed circuit board materials. Like the polyimide resins, polybenzoxazole resins have several drawbacks including poor flexibility because of rigidity, and difficulty to use because of high Tg, and low solubility in organic solvents.